title: Age-related changes in topological organization of structural brain networks in healthy individuals.
abstract: The aim of this study was to examine structural brain networks using regional gray matter volume, as well as to investigate changes in small-world and modular organization with normal aging. We constructed structural brain networks composed of 90 regions in young, middle, and old age groups. We randomly selected 350 healthy subjects for each group from a Japanese magnetic resonance image database. Structural brain networks in three age groups showed economical small-world properties, providing high global and local efficiency for parallel information processing at low connection cost. The small-world efficiency and node betweenness varied significantly and revealed a U- or inverted U-curve model tendency among three age groups. Results also demonstrated that structural brain networks exhibited a modular organization in which the connections between regions are much denser within modules than between them. The modular organization of structural brain networks was similar between the young and middle age groups, but quite different from the old group. In particular, the old group showed a notable decrease in the connector ratio and the intermodule connections. Combining the results of small-world efficiency, node betweenness and modular organization, we concluded that the brain network changed slightly, developing into a more distributed organization from young to middle age. The organization eventually altered greatly, shifting to a more localized organization in old age. Our findings provided quantitative insights into topological principles of structural brain networks and changes related to normal aging.
authors.affiliation: Department of Nuclear Medicine and Radiology, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan 980-8575. kaiwu@idac.tohoku.ac.jp
authors.forename: Kai
authors.initials: K
authors.lastname: Wu
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Taki
authors.forename: Kazunori
authors.initials: K
authors.lastname: Sato
authors.forename: Shigeo
authors.initials: S
authors.lastname: Kinomura
authors.forename: Ryoi
authors.initials: R
authors.lastname: Goto
authors.forename: Ken
authors.initials: K
authors.lastname: Okada
authors.forename: Ryuta
authors.initials: R
authors.lastname: Kawashima
authors.forename: Yong
authors.initials: Y
authors.lastname: He
authors.forename: Alan C
authors.initials: AC
authors.lastname: Evans
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fukuda
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology*; D001921:Brain / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D009434:Neural Pathways / Q000473:pathology*; D055815:Young Adult